Jet pumps in refrigeration system



H. J. SCULLEN 2,887,857

JET PUMPS IN REFRIGERATION SYSTEM 3 Sheets-Sheet 1 May 26, 1959 FiledJune 28, 1955 INVENTOR. //z .f' jazz/Z677 BY v 7'07P/VLVS May 26, 1959H. J. SCULLEN JET PUMPS IN. REFRIGERATION SYSTEM 3 Sheets-Sheet 2 FiledJune 28; 1955 May 26, 1959 H. J. SCULLEN JET PUMPS INREFRIGERATIONSYSTEM 3 Sheets-Sheet 3 Filed June 28, 1955 R m m m IVE/SThe present invention relates generally to refrigera tionsystemsoperable at low temperatures. More specifically, the invention relatesto a refrigeration system employing refrigerant-powered booster or sionstages.

In refrigeration systemsvadapted to operate at lowtempre-comp'resperatures, that is, at temperatures'below about-.20 or 40F., it has been necessary .to employ compressors capable of drawing'avacuum on the evaporator coils. In the usual case, in the smallcapacitysystems this has meant the use of one or more stages of positivedisplacement type compressors equipped with efficient metal-tometalsealing means to prevent the entry to the system of air and moisture.With this type of compressor, however, there are practical limits,imposed by the operating characteristics or efliciency of their. valves,tothe vacuum that can be drawn and to the number of serially arrangedstages which can be beneficially employed.

It is an object of this invention, therefore, to provide a refrigerationsystem employing one or more refrigerantpowered booster compressionstages to enable mechanical compressors to reach the desired lowevaporator pressures and temperatures. Y t 1 Another object is toprovide a refrigeration system which incorporates one or morepre-compressionor booster stages powered by high pressure refrigerant toextend the normal operating (temperature) range of. 'a given number ofprimary compression stages.

. Still another object is to provide a refrigeration sys tern in whichone or more expensive primary refrigerati on stages are replaced byinexpensive, refrigerantpowered jet pumps.

Still other objects I and advantages of the present invention will beapparent, or will become'apparent, in the more detailed description ofthe invention to follow and in the accompanying drawings, in which: 1 w.Figure l is a more or less: diagrammatic flow sheet illustrating anoperative elementary refrigeration system employing a singleprimarystage of compression and'a single refrigerant-poweredprecompression stage;

Fig. 2 is a view similar to that of Fig. 1 showing a more completerefrigeration system including a single primary Patented- May 26, 1959les sfeflicient, when operated at other than their normal designtemperature; e

m Fig. 4 is aflow diagram of a complete. refrigeration system of. a typeusually employing two primary compression stages, the figure in thiscase illustrating one such primary. stage replaced by tworefrigerant-powered j'et booster'pumps operating in series flowrelation, with one of the booster pumps being powered in part, at least,by flash gas and flash gas condenser vapors and, in part, by highpressure refrigerant from the preceding booster; Fig.5 is.;alcompleteflow diagram and wiring diagram of a refrigeration system adapted tooperate at extremely low temperatures of 125 F. to 200 F. or lower, Fig.5 in, this case showing three primary stages of compression, assisted orboosted by a single refrigerant-powered jet pump booster unit, thelatter deriving its power from an auxiliary compressor arranged todeliver its full output to the nozzle inlet of the jet booster unit; and

" Fig. 6 is a schematic representation in section of a typical jet pumpof the type employed in the refrigeration systems of Figs. 1 to 5.

,As .is indicated above, the present invention provides a refrigerationsystem wherein one or more refrigerantpowered booster units are employedto improve the vacuum-producing capacity of one or more primary stagesof mechanical compression. The booster units are particularlyeffectivein low temperature refrigeration systems wherein fiash gas orrefrigerant vapors of intermediate pressure (which normally are recycledanyway) are'ffavailable to power the booster unit. Such a lowtemperature refrigerating system, employing a flash gas separator (orexpansion vessel) and/or a refrigerantcooled flash gas condenser isdisclosed in my copending application, Serial No. 26l,3l3, filedDecember 12., 1951, now US. Patent No.-2,714,80'6, August 9, 1955.

Referring ,now to the accompanying drawings, it will be seen that Fig. 1shows an elementary refrigeration system which incorporates fewcontrols, only a length of flow-restricting capillary tubing 10 beinginterposed as a control: in the high pressure refrigerant inlet line 12between the condenser 14 and the evaporator coil 16. The tubing 10 iswrapped around, and in heat-exchange relation with, the suction vaporline 18. A primary compressor 20 is arranged to draw low pressurerefrigerant vapors from the refrigerant suction line 18 and to dischargehigh pressure, compressed refrigerant to the condenser 14 through line22. The refrigerant vapors leaving'the evaporator 16 pass throughsuction line 18 to a jetbooster pump 24 wherein they are pre-compressedto a considerable degree and delivered through line 26 to the jinlet ofthe primary compressor 20. The jet pump compression stage and a pair of'serially-arranged, re-

frigerant-powered jet pump pre-compression or booster stages, the systemalso employing a flash gas separator or expansion vessel located betweentwo lengths of flowrestricting capillary tubing with the hash gascollected in the expansionvessel being recycled to-power one of the,booster stages; j v

Fig. 3 is a :view similar to Figs. 1 and 2 showing-a still more completelow temperature refrigeration system, in

this case employing a refrigerant-cooled flash gas con-- v denser orheat-exchanger located between a pair of flowrestricting capillarytubes, a watery cooled primary condenser, a thermostatic expansion valveand othercontro'ls', the systemin this case being. adjustable. as tooperating temperature, whereas, thO SGJOf Figs. 1 and 2'are com]-paratively constant temperature systems whichb'ecome 24lis powered byhigh pressure refrigerant vapor taken from high pressure line 22 throughline 28.

The jet pump 24is of the injector or ejector type shown Fig. 6 which isessentiallya small 'high pressure jetjor nozzle 30 in axial alignmentwith a larger low'p'ressure nozzle, jet or venturi-like passageway 32.Both' nozzles are housed in a casing 34 provided with a small highpressure nozzle inlet 36, a larger suction inlet38 and a nozzle outlet39. With this type of comp'ressor or'pump asmall quantity of highpressure nozzle gas is fed into the nozzle inlet 36 to aspirate lowpressure gas from the evaporator through suction inlet 38. Thepressurenozzle gas and the low pressure suction gas are mingled in thepassageway 32 so as to exit as a single stream having a pressure higherthan that ofthe suction gas but lower than that of the nozzle gas. Suchadevice is of simple construction and is not appreciably more expensivethan a valve or other similar n lffi a- "result of the operation of thejet pump 24 of Fig.1 is'a'net' increase in the amount of'refri'gerant'handled by the primary compressor 20. In some respects this may beconsidered a net decrease in overall operating efliciency, although inmost cases the primary compressor 20 is capable of handling theincreased volume without material increase in power requirements becausethe refrigerant is supplied to its inlet valves at a higher pressurethan would be the case were it drawing'a vacuum directly on theevaporator coil 16. In more complex I ment compressors could beemployed. As a result, the

net initial cost of the system is reduced since the total cost of thejet pump booster and a single compressor of simple design isconsiderably less than the cost of a single reciprocating compressor andits controls. When the primary compressor is a compressor of highvolumetric elficiency the jet pump booster unit enables the system todevelop much lower evaporator temperatures than without it. In thisrespect a single primary reciprocating compressor having a single jetbooster unit is p capable of approaching the operating range of the muchmore expensive two stage systems. Thus, irrespective of the type ofcompressor employed in the primary conipression stages, the use of asingle refrigerant-powered jet booster pump powered by high pressurerefrigerant provides real initial cost and operating advantages in spiteof a sometimes lowered overall efficiency. Where a low temperaturerefrigeration system is not intended for continuous use, the use of thesystem of Fig. 1' results in an overall reduction in cost.

Fig. 2 demonstrates a more complete single (primary) stage systemincorporating two serially-arranged jet pump booster units 24, 46. Aflash gas separator or expansion vessel 40 is interposed between theflow-restricting capillary tubing 10 and a second length offlow-restricting capillary tubing 42. The tubing 42 is connected inseries with the vessel 40 by line 43 and the vessel 40 is connected inseries with the restrictor tubing 10 by means of line 48 taken off thevessel below the level of the liquid therein. Flash gas evolved by theexpansion of refrigerant This tends to lower the pressure in evaporator16 and increase the flow through restrictor 10. Another result is thatjets 24, 46 and compressor 20 deliver an increased supply of liquidrefrigerant to vessel 40, sometimes causing the liquid level to rise inline 44 wherein the liquid refrigerant is vaporized at a greatlyincreased rate. If desired, line 44 could be placed in a position whereit could be warmed or heated and in this way increase the energy drivingjet 46. This in turn causes jet 46 to further lower the pressure inevaporator 16. Thus, the restrictor 10, vessel 40 and jet 46 combine toprovide a control which is more quickly responsive to the load on theevaporator 16.

Fig. 3 illustrates a still more complete single stage refrigerationsystem which employs a water-cooled condenser 50, a refrigerant-cooledflash gas condenser or heat-exchanger 52, an electrically-operatedthermostatic on-ofi valve 54, three flow-restricting capillary tubes 10,56, 58 and a thermostatically-controlled expansion valve 88. The valves54, 88 are located outside of the space being cooled so as not to bind,seize or otherwise operate inefiectually.

In this system the primary compressor 20 is protected by apressure-responsive on-oif control 60 made respom sive to the pressuresexistent at the outlet of the cornpressor 20 by means of a passageway 62connecting with compressor outlet line 22. High pressure refrigerantflows from the compressor 20 through an oil separator 51,

' having an oil return line 53, and thence through line 22 to'thecondenser 50. The supply of coolant in the latter is controlled by apressure-sensitive bellows 64 connected to the compressor outlet line 22by means of a line 65, the bellows 64 operating a water supply valve 66located in the condenser water inlet line 68. The water leaves in vessel40 is taken off the top of the vessel through line 44 and thence to thehigh pressure nozzle inlet of the first jet booster unit 46. The jetbooster 46 draws low pressure suction vapors from the evaporator outletline 18, compresses them and delivers the gas to inlet of the secondbooster unit 24. The latter further compresses the vapors and deliversthem to primary compressor 20. As before, the second booster unit 24 isdriven 'by high pressure refrigerant taken from the outlet of compressor20 through line 28.

As will appear in Fig. 2, the cooled, high pressure refrigerant leavingthe condenser 14 passes through re-. strictor 42 at a controlled rate toenter the flash gas separator or collector 40. Residual 'heat in therefrigerant is dissipated by expansion in the vessel 40 and is conductedaway in the form of vapor, the latter being taken off the top of thevessel through line 44, :as described above. By the use of such avessel, colder, more completely liquid refrigerant reaches theevaporator and the condenser through line 70. From the condenser 50cooled refrigerant flows through a silica gel drying tube 72 and afilter 74 to the electrically-controlled valve 54. The solenoid of thelatter is controlled indirectly by an on-off thermostat (not shown)having a bulb located in the space being cooled, the thermostat servingto shut off the compressor motor and close valve to prevent draining ofthe condenser 50. From the valve 54 the condensed refrigerant passesthrough line 12, which in this case has two branches 76, 78. A portionof the refrigerant flowing in line 12 enters branch 76 and passesthrough a check valve 80, a. thermostatically-controlled valve 82 havingits hub 84 in heat exchange relation with a condenser return line 86,and thence through a length 56 of restrictor tubing to the coolingjacket of the flash gas condenser or heatexchanger 52. Thus arranged,the supply of refrigerant for cooling the flash gas condenser 52 iscontrolled by valve 82 and restrictor 56, the valve 82 increasing theflow of refrigerant in line 76 in response to higher temperatures inline 86. Refrigerant vapor generated in the cooling jacket is returnedto the inlet side of primary compressor 20 through line 86.

The main stream of refrigerant flowing in branch 78 1 passes through athermostatically-controlled valve 88 having its bulb 90 in heat-exchangerelation with the suction gas line 18. Valves 82, 88 are of theequalizer type and each have their pressure elements connected by aby-pass passageway 92 to a point beyond the restrictors 56, 58. In thecase of valve 88, the passageway 92 may a portion of the energy of theflash gas evolved in the be connected to any point intermediaterestrictors 58 and 10. The main stream of refrigerant flows from valve88 through restrictor 58, a silica gel dryer 94, flash-gas condenser 52,a filter 96, and thence through line 44 to restrictor tube 10 and intothe evaporator coil 16. Any residual superheat or flash gas in therefrigerant is condensed in the condenser or heat-exchanger 52 so thatonly cold, liquid refrigerant enters restrictor 10. Since the restrictor10 and bulb of valve 88 are responsive to temperatures in suction line18 the supply of refrigerant in evaporator 16 is maintained at a correctlevel determined by the setting of valves 54 and 88 and the size andlength of restrictors 58, 10.

In the system of Fig. 3, the jet pump 24 is connected between lines 18,26, as before, and is powered by high pressure refi-igerant supplied bythe primary compressor 20 through line 28. The use of the jet pump 24 inthis system makes the primary compressor 20 operate over a narrowerrange of pressure thereby improving its volumetric efliciency and makingpossible lower temperatures in evaporator 16. If compressor 20 is aneificient reciproeating compressor the system of Fig. 3 can producetemperatures in the evaporator 16 substantially as low as a similarsystem employing two full primary stages of compression. The cost of thesystem of Fig. 3 is lower because of the elimination of one expensivecompressor, its seals and its controls. If compressor 20 is aninexpensive type the resulting system can produce temperatures as low orlower than that obtainable with a system employing a single, highefliciency reciprocating primary compressor without a jet booster.

In Fig. 4 there is illustrated a refrigenation system capable ofproducing extremely low temperatures yet it employs but a single primarycompressor 20. The primary compressor 20 is in this case assisted by twoseriallyarranged jet booster units 100, 102 similar to those describedabove. The second booster jet unit 102 is powered by high pressurerefrigerant taken off the outlet line 22 of compressor 20 through line104 and the first jet booster unit 100 is powered by high pressurerefrigerant taken off the inlet line 112 of the primary compressor 20through line 108. It should be noted, however, that vapors from theflash gas separator 40 are recycled between the booster units, and therefrigerant vapors from the cooling jacket of head-exchanger 52 arerecycled to the inlet line 112 of the primary compressor 20. In thisarrangement, the recycle vapors of both the vessel 40 land the condenser52 are available, .through line 108, at least in part, to power thefirst booster unit 100. I

Thus, suction gas leaves the evaporator 16 through line 18, passesthrough the first jet booster 100, and from "thence it is conducted tothe inlet line 110 of the second jet booster 102. From the second jetbooster' the now considerably compressed refrigerant passes through line106.to the inlet line 112 of the primary compressor 20. The primarycompressor 20 under the control of the "pressure responsive element 60supplies refrigerant through lines and valves, a condenser 50, a flashgas lcondenser 52, and an expansion vessel 40 all similar to thecorresponding elements of the system of Fig. 2. In the system of Fig. 4,however, the flash gas separating Iexpansion vessel or reservoir 40 isconnected in series with ,the flash gas condenser 52 in order to achievea similar type of control. Cooled refrigerant from the refrigerantcooledflash gas condenser 52 passes through dryer 94, filter 96, line 114, aflow-restricting capillary tube 116 and line 118 into vessel 40 whereinexpansion occurs with still further cooling of the liquid. Vaporsliberated in this expansion pass out of the top of vessel 40 throughline 120 through a length of flow-restricting capillary tubing 122Wrapped in heat-exchange relation with the outlet line 110 of the firstjet booster 100 then through acheck valve 124 and thence into line 110.The higher the temperatures in line 110, indicating high demand inevaporator 16, the greater will be the pressure in vessel .40 andthegreater will be the flow of liquid refrigerant from vessel 40 toevaporator 16. The effect of vessel 40 thus is to supply refrigerantunder more precise control to the evaporator coil 16 thereby makingpossible still lower evaporator temperatures. The combination of theflash gas condenser 52, expansion vessel 40 and the two jet boosterstages enables the system of Fig. 4 to reach temperatures substantiallyas low as a similar system -employing two or three full stages ofprimary compression. The initial cost of the system of Fig. 4, however,

is much less since one or two compressors, their motors and their motorcontrols have been replaced by the two inexpensive jet pumps which haveno moving parts and which require no controls. The primary compressor20, as in the systems of Figs. 1 to 3, could be of the rotary typeadapted to operate efiicierrtly at high capacity over a narrow pressurerange.

While the refrigeration systems of Figs. 1 to 4 have employed one ormore refrigerant-powered jet booster pumps as partial or completereplacements for one or more primary stages of compression, primarilywith a view to obtaining low temperature performance at a more modestinitial equipment cost, the jet booster pumps also can be used solely todrive the evaporator operating temperatures to new low levels. In Fig. 5there is illustrated a complete flow and wiring diagram of a lowtemperature refrigeration system operative at temperatures of to 200 F.,the system employing three primary stages of compression, a single jetbooster unit, and a fourth compressor employed solely to power the jetbooster. Since three stages of positive displacement type compressorswill operate at or near the limit of the vacuum-producing ability ofthis type, any further decrease in evaporator temperature will not becommensurate with the cost of adding further stages. The reason for thisis that three such stages are capable of operating near the limit of theefliciency of the type of spring-actuated valves usually employed insuch compressors. When, however, a fourth compressor is connected intothe system as shown so as to power a jet booster, a significant increasein vacuum-v producing ability is realized since the jet pump operateswithout the limitations of valves, manifolds, etc. and is capable ofproducing a higher vacuum.

In the system of Fig. 5, many of the elements correspond -to those ofthe systems of Figs. 1 to 4 and are given the same identifying numerals.As 'shown, the space being cooled is enclosed in a dotted line 130. Thethird or final stage compressor 20 delivers highly compressedrefrigerant through oil separator 51 to line 22 through which it flowsto a water-cooled condenser where it is condensed and liquefied. Theliquefied refrigerant then flows through the drier 72, filter 74,solenoid valve 54 and valves 82, 88 before entering the flash gascondenser or heat-exchanger 52. As inthe system of Fig. 4, a flash gasexpansion vessel is connected in series with the condenser 52 althoughin this case the flash gas and condenser coolant vapors are recycled tothe system directly, and are not employed to power the jet booster.

From the evaporator 16, refrigerant vapor passes into a jet booster pump132 wherein it is pre-compressed and delivered through line 134 to afirst primary compressor 136. The first stage jet booster 132, it shouldbe noted, is powered entirely by high pressure refrigerant deliveredthrough line 138 by a fourth compressor 139. The compressor 139 isconnected to line 134 between the booster 132 and first primary stagecompressor 136. With this arrangement the compressor 139 operates overonly a small pressure differential, which differential is equivalent tothe drop in pressure across jet 132. The first stage compressor 136 alsooperates under a much smaller pres- .sure differential, as do the secondstage 146 and third stage 20. With this arrangement, jet 132 operatesvery effi- .ciently and greatly increases the vacuum drawn on theevaporator. The refrigerant is compressed by compressor 136 anddelivered through line 140 to compressor 146. Together with the fiashgas returned through line 120, the partially compressed vapors arefurther compressed in second stage compressor 146 and delivered throughline 26 and are compressed, along with the second stage vapors in thirdstage compressor 20. In a highly compressed condition, the refrigerantis again delivered to condenser .50 through line 22.

Control of the refrigeration system of Fig. 5 is effected by theelectrical controls system shown at the top of Fig. 5 and including themain on-off solenoid-controlled valve 54 and four pressure-sensitivebellows-type compressor motor controls 60 which control the four 3-phasecompressor motors 158, 160, 162, 164 and protect the compressors againsthigh pressure overloads. The compressor motors have, respectively, motorstarters units 159, 166, 168 and 170. A thermostatically-operated switch172 is provided in series with the third stage motor starter 170 tostart and stop all four of the compressors, the switch 172 beingoperated by a temperature-responsive bulb 174 positioned in closeproximity to evaporator coil 16. Thus provided, thermostat switch 172will start and stop the compressors in response to fluctuations of thetemperature obtaining in the cooled space 130. Since the solenoid ofvalve 54 is in series with switch 172, it will effect correspondingon-off control of the supply of refrigerant to the valves 82, 88.

Electrical energy is supplied to the controls system through 3-phaseleads 176, 178, 180 with a main line switch LS-l being provided to shutthe entire system down when desired. Motors 158, 160, 162, 164 areconnected in parallel across leads 176, 178 and 180 while their starters159, 166, 168 and 170 are in series across the secondary of thetransformer 188. Lower voltage control power is supplied to theoperating coils 181, 182, 184, 186 of, respectively, starters 159, 166,168, 170 and to the other switches, valves, etc. by the transformer 188having the terminals of its primary coil 190 connected across leads 176,178. One terminal 192 of the secondary coil 194 is connected to theoperating coil 186 of motor starter 170 and the other terminal 196 isconnected to a common control lead 198. Each of the serially-connectedmotor starter coils 181, 182, 184, 186 have one of their terminalsconnected to lead 198 through a normallyclosed manual cut-off switch 200and its respective pressure control switch 60 and the other of itstermnials' connected to the preceding starter coil by a lead 202. Thusarranged, the de-energization of one starter coil will deenergize allstarter coils.

With the system shut down the thermostatic switch 172 and motor controls60 will be closed so that upon closure of main line switch LS1 and theindividual switches 200, starters 159, 166, 168 and 170 will beenergized to start all of motors 158, 160, 162 and 164. The compressors139, 136, 146 and 20 immediately start to operate with both ofcompressors 136, 139 at first drawing vapor directly from the suctionline 18 through jet 132. The jet booster 132 soon comes into fulloperation due to the plentiful supply of vapor in the evaporator andsuction line. As the evaporator temperature reaches its control point,however, the supply of refrigerant in the evaporator is reduced and avacuum will exist on the suction inlet of the jet. Under theseconditions'the booster powering compressor 139 will be recirculating arelatively large quantity of refrigerant as compared to the smallquantities being aspirated from the vacuumized evaporator. However, itis this type of large ratio operation, not restricted by limitations ofvalves, which enables the jet pump to operate most effectively inlowering evaporator pressures and temperatures. The inlet valves of thefirst primary compressor 136, therefore, will always operate at aconsiderably higher pressure than if the compressor were directlyconnected to the evaporator.

When, as illustrated in Fig. 5, the three primary compressors are of thereciprocating type, the single jet booster unit 132 and itspower-supplying compressor 139 make it possible for the system tooperate at much lower'temperatures due to the ability of the jet pump todraw a high vacuum. Any of the primary compressors of Fig. could be arotating-vane or gear-type of positive-displacement compressor or evenone of the high speed centrifugal turbine types of compressors which donot operate on the positive displacement principle. Since the system ofFig. 5 can produce evaporator temperatures well below the normal 3-stagelimits it can be appreciated that the cost of such a system is much lessthan that of more com- 8 plicated systems designed for the same extremelow temperature operating range.

What is claimed is:

1. In a refrigeration system including an evaporator, having an inletand an outlet and means including at least one refrigerant compressorand a condenser arranged to supply compressed refrigerant to saidevaporator inlet, the improvement which comprises an expansion vesselconnected between said condenser and said evaporator inlet, a length offlow restricting capillary tubing connecting said vessel with saidevaporator inlet and in heat exchange relation with said evaporatoroutlet, a refrigerant-powered jet pumping means having a nozzle outletconnected to the inlet of said compressor, a suction inlet incommunication with said evaporator outlet, and a nozzle inlet, andpassageway means for conducting refrigerant vapor liberated in saidexpansion vessel to the said jet nozzle inlet of said pumping means.

2. In a refrigeration system including an evaporator, a flash gascondenser arranged to supply cooled refrigerant to said evaporator andhaving a refrigerant-cooled cooling jacket, a main refrigerantcondensing means arranged to supply condensed refrigerant to said flashgas condenser, and at least one mechanical refrigerant compressoradapted to supply high pressure refrigerant to said main refrigerantcondensing means, the improvement which comprises a refrigerant-poweredjet pumping means having a suction inlet communicating with saidevaporator, a nozzle outlet communicating with the inlet of saidcompressor, and a nozzle inlet, and a passageway means connected on oneend with the refrigerant-cooled cooling jacket of said flash gascondenser and on the other end with the nozzle inlet of said jet pumpingmeans.

3. In a refrigeration system including an evaporator, a condenserarranged to supply condensed refrigerant to the inlet of saidevaporator, and at least one refrigerant compressor arranged to supplyhigh pressure refrigerant to said condenser, the improvement whichcomprises a first and a second serially-connected refrigerant-poweredjet pumping means, the suction inlet of the first said jet pumping meansbeing in communication with the outlet of said evaporator, the nozzleoutlet of said second pumping means being in communication with theinlet of said compressor, a high pressure nozzle inlet means for eachsaid jet pumping means, passageway means extending from the outlet ofsaid compressor to the nozzle inlet of one of said jet pumping means,and passageway means extending from the nozzle outlet of said one ofsaid jet pumping means to the nozzle inlet of the other jet pump ingmeans.

4. In a multiple-stage refrigerating system including an evaporator anda refrigerant compressor arranged to supply condensed refrigerant tosaid evaporator, the improvement which comprises a refrigerant-poweredjet pumping means serially-connected to deliver refrigerant to thesuction inlet of said compressor, said jet pumping means having asuction inlet in communication with said evaporator, a nozzle outlet incommunication with the said inlet of said compressor, and having anozzle inlet, and a second refrigerant compressor having a suction inletin communication with the inlet of the first mentioned compressor andwith said nozzle outlet of said jet pumping means and having arefrigerant outlet in communication with the said nozzle inlet of saidjet pumping means.

5. In a refrigeration system, the combination comprising an evaporatorhaving an inlet and an outlet, a refrigerant expansion vessel having anoutlet for cooled liquid refrigerant in communication with the inlet ofsaid evaporator and having an outlet for refrigerant vapors, and aninlet for condensed refrigerant, means including a mechanicalrefrigerant compressor and a condenser for supplying condensedrefrigerant to said condensed refrigerant inlet of said vessel and asuction inlet communicating with said outlet of said evaporator, arefrigerantpowered jet pumping means serially-arranged with a suctioninlet in communication with the said outlet of said evaporator and anozzle outlet in communication with the said inlet of said compressorand having a nozzle inlet for the reception of high pressurerefrigerant, passageway means connecting the outlet of said compressorwith the said nozzle inlet of said pumping means, and passageway meansconnecting the said outlet for refrigerant vapors of said expansionvessel with the said suction inlet of said jet pumping means.

6. In a refrigeration system, the combination comprising an evaporatorhaving an inlet and an outlet, a refrigerant-cooled, jacketedheat-exchanger for supplying cooled liquid refrigerant to saidevaporator inlet, means including a mechanical refrigerant compressorhaving an outlet and a condenser for supplying condensed refrigerant tosaid heat-exchanger and its jacket and an inlet communicating with theoutlet of said evaporator, a pair of refrigerant-powered jet-typepumping means in series flow arrangement, a first of saidserially-arranged pumping means having a suction inlet communicatingwith the outlet of said evaporator, the second of said serially-arrangedpumping means having a nozzle outlet communicating with the said inletof said compressor, each said pumping means having a nozzle inlet forreceiving high pressure refrigerant, passageway means connecting theoutlet of said compressor with the nozzle inlet of said second jetpumping means, passageway means connecting the said nozzle inlet of saidfirst jet pumping means with the said outlet of said second jet pumpingmeans, and passageway means connecting the jacket of said heat-exchangerwith a point intermediate said first and second jet pumping means.

7. In a refrigeration system including an evaporator, having an inletand an outlet and means including at least one refrigerant compressorand a condenser arranged to supply compressed refrigerant to saidevaporator inlet, the improvement which comprises an expansion vesselconnected between said condenser and said evaporator inlet, restrictionmeans connecting said vessel with said evaporator inlet, arefrigerant-powered jet pumping means having a nozzle outlet connectedto the inlet of said compressor, a suction inlet in communication withsaid evaporator outlet, and a nozzle inlet, and passageway means forconducting refrigerant vapor liberated in said expansion vessel to thesaid nozzle inlet of said jet pumping means.

References Cited in the file of this patent UNITED STATES PATENTS2,195,604 Taylor Apr. 2, 1940 2,513,361 Rausch July 4, 1950 2,683,361Ridgley July 13, 1954 FOREIGN PATENTS 660,771 Great Britain Nov. 14,1951

